Summary: A new classic of war fiction in the making, this kaleidoscopic, empathetic portrait of Australian POWs working on the Burma Death Railway during World War II would be a deserving Man Booker Prize winner.

The Narrow Road to the Deep North is the title of both Flanagan's Booker Prize-longlisted sixth novel and a book by seventeenth-century Japanese poet Basho. Poetry irradiates this often bleak story of Australian POWs building the Burma Death Railway during the Second World War, presenting beauty and love as counterpoints to gory descriptions of suffering and inhumanity.

Dorrigo Evans was born in Cleveland, Tasmania, in the years just after the First World War, and overcame his lower-class origins to become a surgeon. In the novel's present day, he is a 77-year-old war hero writing a preface to the sketchbook a fellow POW kept on the Death Railway. 'Horror can be contained within a book, given form and meaning. But in life horror has no more form than it does meaning,' he eventually writes.

That is Flanagan's challenge here: to give literary form to the horrors of war, without resorting to despair or simple us-versus-them dichotomies. He maintains a careful balance of sympathy by shifting between the perspectives of the Australian POWs and their Japanese captors, and by setting up a tripartite structure: a before, during and after that shows how war affects the whole of life. The narrative is quite intricate, slipping between past and present.

Sustaining Colonel Evans throughout his captivity is a secret passion for his uncle's wife, Amy. In alternating chapters, the gruesome reality of camp life contrasts with the optimism of this budding love affair. Sections from Amy's perspective are particularly strong, and the subplot of a fateful romance recalls Sebastian Faulks's Birdsong. That and Ford Madox Ford's Parade's End are chief points of reference – especially how the Ford trilogy showcases the build-up and aftereffects of the war as well as its terrible heart.

Part Two zeroes in on day-to-day experience in the camp. It is a grim reality of cholera, savage beatings and near-starvation. In one memorable scene, Dorrigo tries to save a soldier's life by performing an emergency amputation; those who do not survive are burned on pyres. There is some standard barracks humour, but pleasures are rare: a tin of condensed milk, a hidden egg. Whereas the first third of the novel is incredibly powerful – almost a stand-alone novella – this second part drags and might have been shortened. Still, it presents a stark picture of camp life: 'What was a prisoner of war anyway? Less than a man, just material to be used to make the railway, like the…steel rails and dog spikes.'

The aftermath of the war merits an entire third of the text – perhaps an unusual decision, but one that ensures readers get the full story of how it affected everyone involved. Dorrigo returns to Ella, his fiancée, and enters a loveless marriage. One of the Korean guards from the camp is prosecuted as a war criminal. Some of Dorrigo's comrades turn to drink; he also learns about his brother Tom's illegitimate son. A few of the vignettes seem irrelevant, including an action sequence involving a bush fire. I wondered whether it was all necessary, or whether Flanagan was just having trouble deciding where to end.

Major Nakamura's 'after' story is the most fascinating. He was among the 'better' Japanese; though he sanctioned brutality and spouted propaganda about the glory of the Empire, he at least treated Dorrigo as an equal. After the war, we find Nakamura in a deserted Tokyo, fearing arrest and scrounging food. Degrees of violence and culpability come into question when Nakamura meets a doctor who performed live dissections on American airmen. Even this hardened war criminal finds some acts unimaginable. 'One cannot point, one cannot say this man here is a man and that man there is a devil,' he declares. Indeed, that is Flanagan's triumph: illustrating how nuanced the situation is, and how widespread the guilt.

An absence of speech marks can at times foster detachment from the characters, but the writing is unfailingly beautiful. Japanese death poems and Tennyson's 'Ulysses' weave through as refrains, and the language is lyrical even when describing atrocities: corpses are 'drying dark-red meat and fly-blown viscera'. As the poem by Issa used as an epigraph reads, 'In this world / we walk on the roof of hell / gazing at flowers' – finding whatever shards of beauty and love we can, even in nightmarish circumstances. War threatens human dignity, but people are never just a collection of body parts.

Flanagan's father, a survivor of the Burma Death Railway, died on the day Flanagan finished writing this novel. 'A good book, [Dorrigo] had concluded, leaves you wanting to reread the book. A great book compels you to reread your own soul.' A new classic of war fiction in the making, this kaleidoscopic, empathetic novel will inspire much soul-searching: a great book indeed, and a frontrunner for the 2014 Man Booker Prize.